1. Field of the Invention
This invention relates to a method for preparing a rosuvastatin calcium intermediate, and more particularly to a method for preparing a compound of formula I.

2. Description of the Related Art
Rosuvastatin calcium, with chemical name of (3R,5S,6E)-7-[4-(4-fluorophenyl)-6-isopropyl-2-(N-methyl-N-mesyl amino)-5-pyrimidine]-3,5-dihydroxyl-6-heptenoic acid calcium, is a new statin drug including a single enantiomer prepared by total synthesis, and belongs to HMG-CoA reductase inhibitors. Rosuvastatin calcium can lower rising LDL-cholesterol, total cholesterol, triglyceride, and apoprotein B, and increase HDL-cholesterol. Rosuvastatin calcium is used for comprehensive treatment of patients with primary hypercholesterolemia, combined hyperlipidemia, or homozygous familial hypercholesterolemia. Its chemical structural formula is as follows:

A typical preparation method of rosuvastatin calcium is as follows:

However, the method is disadvantageous in the following aspects: 1. DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) is necessary in the process, but DDQ is extremely toxic; 2. Raw materials, such as 4-methylmorpholine-N-oxide, TPAP (tetrapropylammonium perruthenate), and DIBAL-H, are expensive; 3. DIBAL-H reacts at a low temperature about minus 70 degrees centigrade to minus 40 degrees centigrade, thereby resulting in a high energy consumption and production costs, which is not suitable for large-scale industrial production; and 4. The yield in the reaction is low.